It’s a widely known fact that weeds are unsightly, troublesome plants. In lawns, they disrupt the lush, green, carpet effect we work to achieve. Even worse are the weeds that invade vegetable gardens where they reduce yields and quality of produce. Weeds compete for available moisture, nutrients, sunlight, and growing space.  They also serve as cover for insects, alternate hosts for diseases, and hiding places for rodents and snakes. Controlling weeds is vital step in maintaining a productive vegetable garden.

This article addresses several methods, including cultural techniques, use of mulch and the use of herbicides, which when combined can reduce weed pressure.

Soil amendments can work great, but be careful with soil amendments. Although barnyard manure is a good fertilizer source, it also contains weed seeds. Make sure your manure is fully composted before applying it to your garden plot. Plant crops at the proper depth in soil that has been tested and given appropriate amounts of lime. Vegetables that get a healthy start in good soil can often suppress weeds through quick growth and heavy vegetation which shades the soil.

Vegetables good at suppressing weeds through shading include beans, squash, tomatoes, potatoes, pumpkins, sweet corn and cucumbers. Avoid watering the entire garden which promotes excessive weed growth. Try using drip irrigation to place water directly at the plant. Hoeing and pulling weeds or cultivating with a rotary tiller is labor intense but very effective in controlling weeds. Weeds should be removed when they are less than 3 inches tall and as often as every two weeks. Avoid deep cultivation after the garden has been established since this will pull new weed seeds to the surface and possibly damage vegetable roots.

Mulches are one of the best ways to prevent weed germination.  You can choose either organic or inorganic mulches. Both are equally effective, however inorganic mulches will need to be removed from the garden each season, while organic mulches can be left or tilled into the soil. Commonly used organic mulches include bark chips, rotted sawdust, compost, newspapers (shredded or in layers), and straw. They should be applied three to four inches deep around the base of vegetable plants. Organic mulches should be applied in May or June after the soil has warmed.

Plastic is the most frequently used inorganic mulch. Black plastic can be laid in early spring to help increase soil temperatures and thus planting time. Fertilizer should be worked into the soil prior to laying the plastic.  After it has been in place for about one week, transplant vegetables into holes cut in the plastic at recommended spaces. Clear plastic can be used in the summer. Laid on the soil during hot temperatures, it will act as a greenhouse encouraging weed seeds to emerge.  Weeds trapped under the plastic will quickly die from the heat. In some cases, temperatures can become high enough to kill many non-germinated weed seeds in the top two inches of soil.

A fabric mulch is also highly effective in preventing annual weeds and could be applied in the spring. It allows air and water to pass through to the soil but prevents weed seedlings from becoming established. Cost is often prohibitive for fabric mulch in most home gardens.

Before crops are planted a non-selective herbicide such as Round-up can be applied to kill existing weeds (fall, late winter, or early spring). Round-up should not be used when vegetables are present since damage can occur. Trifluralin (Treflan) can be used as a pre-emergence herbicide to control weed seedlings in gardens. This product is available in granular or liquid form but is not safe for all vegetables.  Read the label before use.  Emerged grasses less than 4 inches tall can be controlled with a post-emergence herbicide containing sethoxydim (Poast). As with Treflan, this product is not safe for all vegetables and you should consult the label.

Combining cultural techniques, mulches, and herbicides will help vegetable crops perform better and increase yields, but perhaps the most important benefit is that it reduces the time you have to spend pulling weeds in your garden this year.

For more information, contact me at the Henderson County Cooperative Extension; we are happy to help!

Contact Andy Rideout at the Henderson County Extension Office at pandrewrideout@uky.edu, at 270-826-8387 or stop by the Henderson County Cooperative Extension Service at 3341 Zion Road, Henderson, KY for more information.